1. Field of the Invention
The present invention relates to an automatic transmission for automobiles and, more particularly, an improvement with regard to the convenience for assembly of an automatic transmission of the type which comprises a fluid torque converter, an overdrive means and an auxiliary reduction gear means.
2. Description of the Prior Art
An automatic transmission for automobiles generally comprises a combination of a fluid torque converter and an auxiliary reduction gear means which effects various reduction gear ratios wherein the top gear is a direct connection. Particularly when an automatic transmission incorporates an overdrive means for effecting an overdrive gear ratio, the overdrive means is generally attached to the output side of the auxiliary reduction gear means because this arrangement requires only a slight and easy modification in the design of the standard automatic transmission including a fluid torque converter and an auxiliary gear means. However, when the overdrive means is incorporated in the rear output end portion of the transmission, it receives an input power in a higher torque condition effected by the auxiliary reduction gear means, whereby the overdrive means must be designed to have stronger and heavier gears, friction engaging means and other associated elements. This is a disadvantage in view of the dimensions and costs. Furthermore, although the design alteration in the automatic transmission itself may be small, such an enlarged transmission often requires a large modification in the design of the vehicle body.
In view of the above-mentioned disadvantages, it has been contemplated to incorporate an overdrive means between a fluid torque converter and an auxiliary reduction gear means, i.e. at the input side of a reduction gear means. However, this arrangement requires a great deal of design alteration with regard to the conventional part, and particularly it has been considered difficult to accomplish a fine alignment in the assembly of a torque converter housing enclosing the fluid torque converter, a transmission case enclosing the auxiliary gear means and a newly interposed overdrive case enclosing the overdrive means.